I can see how this is a very frustrating situation for you, and from what you are saying, it does sound like you are trying to help and show your love and concern for her. For some reason, she's interpreting your concern as controlling - her reaction does not seem to be normal or consistent with the situation you've described.
Based on what you've said (the drug use, the behavior, the irrational thinking, etc), it sounds like she might have borderline personality disorder
- also referred to as BPD (although, of course, I can't say for sure without meeting her in person - she'd need to see a psychiatrist or another mental health professional to have an evaluation and obtain a proper diagnosis). These types of patterns are very common in patients with BPD. It's a much more common disorder in women than in men, and it's also extremely under-diagnosed because people with the disorder don't want to admit that they have a problem and have a very hard time asking for help.
Everything that you're describing points to this disorder - and it can be very difficult to have a functional, healthy relationship with a person like this - although it is certainly possible. I'd like to provide you with more information about it and suggest a few books/articles you can read to help you deal with her behavior (although again, I just want to reiterate that I can't provide a diagnosis on this website, so this is just for informational purposes). I think you'll find this helpful, however.
This is general information about symptoms (you can click the menu on the left of the page for more info):
Randi Kreger is a researcher who pioneered work on BPD and she wrote a book to help loved ones of people with BPD deal with their behavior, it's called "Stop Walking on Eggshells". You can visit her website for more information as well:
I would say that you have to protect yourself in this situation and realize that her behavior is not always going to be rational even when you're trying your best to be helpful. It might be a good idea for you to think about seeking counseling for yourself, just to help you cope and deal with the situation if you plan to stay in the relationship. You can make it work, but it's best if she seeks treatment and you learn the skills you need to manage being in a relationship with someone like this.
I hope that helps. Best of luck, and please let me know if you need any additional assistance.